Foam generating apparatus

ABSTRACT

A foam generating nozzle is made either as an attachment to an existing liquid spray nozzle unit or as a pre-manufactured assembly and includes a foam-generating section having a pressure-reducing passageway including a preferably sharply outwardly tapering portion leading to a venturi-forming throat portion, and adapted to receive the entire variable angle unaerated liquid spray issuing from an inlet orifice. Air inlet ports are provided communicating with the pressure-reducing passageway, through which ports air is drawn by the reduced pressure caused by the pressure-reducing passageway. Greatly increased foaming action is achieved by providing an enlarged outlet passageway at the outlet end of the venturi-forming throat portion of the foam generating section, where the outlet passageway preferably has a length to diameter ratio in the range of about 10 to 16, but in any event falling in the range of from about 7 to 20.

United States Patent [191 Lamz et al.

1 51 Nov. 11, 1975 FOAM GENERATING APPARATUS [73] Assignee: Chemtrust Industries Corporation,

Franklin Park, Ill.

[22] Filed: Jan. 14, 1974 [2]] Appl. No.: 432,949

[52] US. Cl. 239/428.5; 239/432; 169/14 [51] Int. CI. B05B 7/00 [58] Field of Search 169/14, 15; 239/343, 370,

518.460 3/1955 Italy l69/l5 Primary E.\'ttmtner-John J. Love Attorney. Agent, or Firm-Wallenstein, Spangenberg, Hattis & Strampel 5 7 ABSTRACT A foam generating nozzle is made either as an attachment to an existing liquid spray nozzle unit or as a premanufactured assembly and includes a foam generating section having a pressure-reducing passageway including a preferably sharply outwardly tapering portion leading to a venturi-forming throat portion. and adapted to receive the entire variable angle unaerated liquid spray issuing from an inlet orifice. Air inlet ports are provided communicating with the pressure-reducing passageway. through which ports air is drawn by the reduced pressure caused by the pressure-reducing passageway. Greatly increased foaming action is achieved by providing an enlarged outlet passageway at the outlet end of the venturi-forming throat portion of the foam generating section, where the outlet passageway preferably has a length to diameter ratio in the range of about 10 to l6. but in any event falling in the range of from about 7 to 20.

9 Claims, 12 Drawing Figures [56] References Cited UNITED STATES PATENTS 2,630,183 3/1953 Foutz 169/15 3,388,868 6/1968 Watson et al 239/590.3 x 3.547.200 12/1970 Hout 169/15 3.701.482 10/1972 Sachnikn. 169/15 3,784,111 1/1974 Piggott -39/5903 FOREIGN PATENTS OR APPLICATIONS 875,877 10/1942 France 1. 169/15 627.285 8/1949 United Kingdom 169/15 0" D; 9 I A\\\ US. Patent Nov. 11,1975 Sheet10f3 3,918,647

FOAM OWL/TY U.S. Patent Nov. 11,1975 Sheet3of3 3,918,647

FIG. 88

FIG. 8A

.. 27" Q AREA .1 AjED FIG. 9A

FIG. 10

1b 1.5mm 1o DIAMETER R4710 FOAM GENERATING APPARATUS BACKGROUND OF THE INVENTION The present invention relates to foam generating nozzles and foam generating systems utilizing the same, and which, while having application for the dispensing of a wide variety of chemicals, has its most important application in the dispensing of cleaning chemicals.

The application of chemicals in a foamed condition is frequently desirable for a number of reasons, Thus, it permits the application of chemicals with lower spray rates and active chemical content with the advantage of reduced costs. Also, especially when spraying vertical or downwardly facing horizontal surfaces, maximum contact time of the foamed material on the surface involved is achieved. Additionally, it eliminates the health and safety hazards caused frequently by liquid sprays which by splashing or otherwise forms tiny droplets or a fine mist which is inhaled and strikes the eyes to cause great discomfort and sometimes serious harm to the persons involved. The application of the material in a foamed state reduces or eliminates the tiny droplets or mist formation which causes these health and safety hazards.

The application of agricultural chemicals by spraying from airplanes and the like by foam generating equipment including a nozzle unit which mixes air with the liquid chemical is well known. Occasionally, cleaning chemicals have been applied by foam-producing aerosol and other type dispensing units.

Many materials such as soaps can be readily foamed by mild agitation, and other materials are more difficult to apply in the foamed condition. Foaming agents can sometimes be added to the latter materials to increase their foamability when agitated by passage through an aerosol nozzle or when mixed with air in an aerating nozzle.

The type of foam achieved by a particular foam generating nozzle unit is a function of a number of factors, such as the nature of the material being sprayed, the pressure of the material when applied to the nozzle unit and the design of the nozzle unit. Also, the desired consistency of the foam to be developed by a particular nozzle unit depends upon the particular application involved. Thus, for applications involving a prolonged desired retention on vertical and downwardly facing horizontal surfaces, it is usually desirable to apply the material involved as a thick foam. Also, it has been discovered that the penetrating power of a material applied to a porous surface is often maximized by applying the material in a foamed condition with minimum sized foam bubbles, which is generally characteristic of a thick foam.

Foam generating nozzle units heretofore developed have been less than completely satisfactory for a number of reasons, including their complexity and high cost, and their inability to create a thick foam with a wide variety of foamable chemicals and inlet pressures.

Some examples of foam generating nozzle units heretofore developed are shown in the following patents:

US. Pat. No. 3,701,482 U.S. Pat. No. 3,446,485 U.S. Pat. No. 2,766,026 U.S. Pat, No. 2,556,239 U.S. Pat. No. 3,094,171

One form of foam generating nozzle unit heretofore developed and which is disclosed in U.S. Pat. No. 3,701,482 includes at the inlet end thereof one or more small orifices through which unaerated liquid passes at a relatively high velocity into the relatively large inlet chamber of a venturi unit having a gradually converging portion communicating with a venturi-foaming throat which communicates with an expansion chamber at the outlet end of the nozzle unit. Air ports are lo cated just beyond the high velocity nozzle. through which ports air is sucked by the low pressure developed in the venturi-forming throat. The design of this nozzle unit is such that significant foaming action occurs in only the expansion chamber. The rate of foaming was thought to be a function mainly of the relative size of the throat of the nozzle unit and the total area of the high velocity orifices. The change in foaming action, therefore, required a change in the size of the orifices which did not lend such units to a practical progressive adjustment of the degree of foaming action obtained.

There has been developed by another inventor a foam generating nozzle unit with a progressive control over the degree and quality of the foaming action in a foam generating nozzle unit of the air aspirating type (i.e. a unit having an orifice opening onto a pressurereducing passageway which creates a low pressure which draws air into the passageway through air ports provided thereat). The progressive control is achieved by a manually operable control which varies progressively the angle of divergence of the stream emanating from the orifice so as to vary the area of the pressure reducing passageway initially struck by the stream. The pressure reducing passageway most advantageously comprises an outwardly tapering portion terminating in a throat portion. In such case, a narrow stream flowing from the orifice which strikes only the outer end portion of the walls of the throat portion of the nozzle (or passes therethrough without striking the throat walls) will produce little or no foaming action. Progressively wider diverging streams flowing from the orifice striking greater extents of the throat and tapered portions of the pressure reducing passageway of the nozzle unit produce greater foaming action and hence thicker foams. A thick foam, however, does not necessarily produce the most desirable stream quality because the rate of foam application can reach an undesirably low value when the angle of divergence of the stream increases well beyond a desired intermediate value.

SUMMARY OF THE INVENTION The present invention has particular, but not its only, application to an adjustable foam nozzle unit like that just described. Thus, in accordance with the invention, it was discovered that agreatly increased foaming action is achieved in the already foamed stream issuing from the throat portion of the air pressure reducing passageway by adding thereto an expansion chamber (which has little or no effect in creating an improved foaming action when the liquid discharge from the throat portion has not yet been foamed). Thus, the main benefit of the expansion chamber is in its combination with a foam producing nozzle in advance of the same. In the adjustable nozzle unit, an improvement of foam quality was achieved for length to diameter ratios of from 7 to about 20 with ratios of 10 to 16 being preferred. If the length to diameter ratio of the expansion chamber of the expansion chamber is increased materially beyond the upper end of the former range. the frictional forces involved reduce the velocity of the foamed material discharged from the end of the nozzle attachment to a point where an inadequate quantity of the material will reach the surface to be cleaned.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a unique mobile foam dispensing unit having particular utility for dispensing cleaning chemicals and which includes a unique foam generating nozzle attachment which converts a conventionaltype liquid spray nozzle into a foam generating nozzle;

FIG. 2 shows a fragmentary plan view, partly broken away. of the mobile unit of FIG. 1'.

FIG. 3 illustrates a conventional pressurized tank sprayer with the unique foam generating nozzle attachment attached thereto;

FIG. 4 is an enlarged side elevational view of the foam generating nozzle attachment units shown in FIGS. 1-3;

FIG. 5 is an exploded partial longitudinal sectional view of the foam generating nozzle attachment shown in FIGS. 1-4 separated from a portion of a conventional liquid spray nozzle unit to which it is attached;

FIG. 6 is a transverse sectional view through FIG. 5 taken along section line 6-6;

FIG. 7 is a longitudinal sectional view through the attachment of FIGS. 4 and 5 when attached to a portion of the liquid spray nozzle unit shown in FIG. 5;

FIGS. 8A and 88 respectively show the condition of the foam applied by a foam generating nozzle unit of the present invention adjusted to apply a thin foam as the foam initially strikes a vertical wall surface and a number of seconds thereafter;

FIGS. 9A and 98 respectively show the condition of the foam applied by a foam generating nozzle unit of the present invention adjusted to apply a thick foam as the foam initially strikes a vertical wall surface and a number of seconds thereafter;

FIG. 10 illustrates a curve showing the variation in foam quality with the length to diameter ratio of the expansion chamber portion of the nozzle units of FIGS. 19.

. DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Referring now more particularly to FIGS. 1 and 2. a portable mobile cleaning unit 2 is there shown which is used to apply a cleaning chemical or the like in a foamed condition. The mobile cleaning unit 2 resembles in a general way a lawn mower in that it includes a low profile base and housing assembly 4 mounted on wheels 5 and a tubular structure generally indicated by reference numeral 7 attached to the sides of the rear portion of the base and housing assembly 4 and extending upwardly and rearwardly where it terminates in a handle grip portion 7a which can be comfortably grasped to manually propel the mobile cleaning unit to various points in or around a building or other structure to be cleaned.

The base and housing assembly 4 comprises a base structure 4 including a horizontal support platform 6 from the margins of which upwardly extend end walls 8-8 and side walls 10-10 forming an open top boxlike structure. On the rear portion of the support platform 6 is an electric motor 12 (or other suitable source of motive power like an internal combustion engine).

Where an electricmotor is utilized. a power cord 13 is provided which extends to a suitable power on-off switch 15 (shown in the drawings at the top of the base and housing assembly 4) and then to the electric motor 12. The electric motor 12 has a horizontal shaft 12a extending to a conventional pump unit 14, which has an inlet 14a from which extends a flexible conduit 16 passing through a fitting 18 into the bottom portion of a drum or other container 20 containing the cleaning chemical to be dispensed. The liquid in the drum 20 may be any suitable foamable liquid. and will generally include a water soluble cleaning material and possibly other additives. together with a foaming agent. where necessary. to provide a foam when the mixture delivered from the drum 20 is agitated in a manner to be explained.

The drum 20 is confined by a vertical cylindrical wall 21 extending downwardly from the inclined wall 23 of a housing 412 to engage the platform 6 to form a well in which the drum 20 is held in place on the platform 6. The well-forming wall 21 together with the rest of the housing isolates the motor and pump from the exterior thereof. The housing 4h may be a synthetic plastic molded body including. in addition to the inclined wall 23 from which the depending cylindrical wall 21 extends. side walls 2525, a rear top wall 27, a rear wall 29 bridging the rear top wall 27 and the side walls 2525, and a narrow flange 31 depending from the front margin of the inclined wall 23. The housing 4b may be secured to the walls 8-8 and 1010 of the base structure 40 in any suitable way. such as by screws passing through housing flange 31, side walls 2525 and rear wall 29 and threading into the walls 88 and 1010 of the base structure.

The pump 14 has an outlet 14b connected by a flexible conduit 22 to a handle and nozzle assembly generally indicated by reference numeral 24. The handle and nozzle assembly 24 includes a handle portion 24a from which extends a lever 26 which, when depressed opens a valve (not shown) to permit passage of liquid into a rigid tube 24!) terminating in a discharge nozzle assembly generally indicated by reference numeral 33. The handle and nozzle assembly 24 may be anchored in any suitable way to the tubular structure 7, such as by a suitable clamp 35 attached to the tubular structure.

When the electric motor 12 is operating. the pump 14 will be rotated to draw fluid from the conduit 16 and force fluid into the conduit 22. When the lever 26 of the handle and nozzle assembly 24 is depressed to open the valve associated therewith. the fluid will flow through the discharge nozzle assembly 33. When the lever is released. the valve involved will be closed. and, to prevent undue back pressure on the pump 14. a normally closed pressure relief valve 37 associated with the pump will open to direct fluid which cannot flow through the outlet conduit 22 to some other location. which may be through a conduit (not shown) extending back into the drum 20 or, as shown. to the inlet 14a of the pump 14.

As shown in FIG. 5, the discharge nozzle assembly 33 illustrated comprises a well known nozzle part 330 which. together with another well known spray angle adjusting member 330 to be described, forms a conventional non-foaming liquid spray nozzle of the type sold by the Chapin Manufacturing Works of Batavia. N.Y. The spray angle adjusting member 33c is rotatably adjustably supported upon the nozzle part 33a and produces a diverging spray pattern issuing from a discharge orifice 42 of the member 330 with an angle of divergence depending upon the particular rotational position of the member 33c upon the valve part 33a.

One aspect of the present invention is the inclusion of a very efficient and adjustable foam generating nozzle attachment 33b in the assembly of the nozzle part 33a and spray angle adjusting member 330. Because of the efficiency of foam generation of the foam generating nozzle attachment 33b, the cleaning material contained in the drum can cover and clean effectively an extremely large area, such as an area 6 or more times that which could be covered by a non-foaming liquid spray system. This is what makes the lawn mower sized mobile cleaning unit 2 useful and practical for dis pensing maintenance chemicals.

Before describing the foam generating nozzle attachment 33b, reference should be made to FIG. 2 which shows another application of this nozzle attachment to a tank sprayer 2 which has a conventional construction except for the attachment 33b used therewith. The tank sprayer 2 has the usual metal tank 2a with a hand pump handle 2b extending from a cover 20 which is sealingly applied in an opening in the top of the tank 2a by a rotational motion applied to the cover. When reciprocated, the handle 2b builds up air pressure within the tank 2a". A flexible outlet conduit 22 extends through a fitting 18' in the tank 2a and terminates in a handle and nozzle assembly 24 identical to that used with the mobile cleaning unit in FIG. 1. Accordingly, the handle and nozzle assembly 24 includes a handle portion 24a with a lever 26 for opening and closing a valve which effects the passage or stoppage of flow of fluid forced into the conduit 22 by the pressure of the air in the tank 2a.

The aforementioned nozzle part 33a to which the foam generating nozzle attachment 33b is connected may take a variety of forms. However, as illustrated, the nozzle part 33a includes a neck portion 28 (see FIGS. 4-7) defining a passageway 30 communicating with the metal tube 24b and terminating in a series of laterally facing ports 32 which direct the liquid passing through the nozzle part 33a in a lateral direction. In the nozzle part 33a (manufactured by the Chapin Manufacturing Works), the end portion of the neck 28 thereof is provided with angular grooves or indentations 34 The aforementioned spray angle adjusting member 33c has a cylindrical passageway 36 therein which at one end opens for the full extent thereof into the outside of the member and at the other end joins a tapered passageway 37 which terminates in a small discharge orifice 42 previously mentioned. The fully opened end ofthe passageway 36 of the spray angle adjusting member 330 is internally threaded at 38 to permit the member 34 to be threaded around an externally threaded portion 28a of the neck portion 28 of the nozzle part 3311. As the spray angle adjusting member 34 is rotated upon the neck portion 28 to a different axial position thereon, the spacing between the discharge orifice 42 and the laterally facing ports 32 varies which, in turn, varies the angle of divergence of the unfoamed liquid stream emanating from the discharge orifice 42.

It was discovered that the unfoamed liquid spray emanating from the dischargeorifice 42 can be converted into a foamed state where the thickness thereof is a function of the angle of divergence of the liquid stream issuing from the discharge orifice 42 by the addition of the foam generating nozzle attachment 331) which, as illustrated, is mounted around the outside of the spray angle adjusting member 34. In the form of the invention illustrated the foam generating nozzle attachment 33b is permanently anchored around the spray angle adjusting member 34. In the most preferred form ofthe invention, the foam generating nozzle attachment 331; has a hollow cylindrical body 40 which has a longitudinal open ended passageway 40a therein. The spray angle adjusting member 330 is press fitted within one end of the passageway 40a. The cylindrical body may be knurled at a point 401) therealong so it can be readily grasped and rotated to vary the position of the spray angle adjustment member 33s on which it is mounted.

At a point preferably immediately in front of the discharge orifice 42, the cylindrical member 40 is provided with one or more, preferably four, laterally facing circumferentially spaced air ports 43 which pass through the walls of the member. Secured in any suit able way within the cylindrical body 40 at a point immediately in front of the air ports 43 is a pressurereducing member 44 in which is formed a pressure reducing passageway having an: outwardly tapering portion 4611 which preferably at its wide end has a width approximately equal to the internal diameter of the cylindrical body 40 and at its narrow end terminates in a cylindrical throat portion 46!). When liquid flows through the air pressure reducing passageway of the member 44, the resultant reduced pressure causes air to be aspirated into the liquid stream through the air ports 43. Foaming of the aerated foamable material results from the turbulence created within the air pressure reducing passageway of the member 44, and the degree of this turbulence and the thickness of the foam generated thereby was unexpectedly discovered to be a function of the angle of divergence of the stream issuing from the discharge orifice 42 This stream is directed against progressively increasing areas of the air pressure reducing passageway of the member 44 as the angle of divergence of this stream is accordingly increased from a generally thin roughly cylindrical shape (i.e. only slightly diverging) to a widely diverging shape. In the former case, little or no foaming action occurs since the thin stream' will pass through the throat portion 46b of the pressure reducing passageway of the member 44 or will strike only the rear end portion thereof. As the spray angle adjusting member 330 is progressively rotated to increase the angle of divergence of the stream, the stream will first strike progressively increasingly larger areas of the throat portion 46b and then progressively increasing areas of the outwardly tapering portion 46a of the pressure reducing passageway, which progressively increases the turbulence applied to the aerated liquid stream. It is believed that this turbulence is accentuated by the fact that the outwardly tapering portion 460 is sharply tapered so as to subtend an angle of about at least 60, where the walls thereof incline at least 30 to the longitudinal axis, and preferably about rather than gradually tapered, although the broader aspects of the invention envision a gradual taper.

The quality of the foam issuing from the outlet end of the throat portion 46b of the pressure reducing passageway of the member 44 is believed to reach an optimum value when the angle of divergence of the stream issuing from the discharge orifice 42 is sufficiently large as to strike the defining walls of the tapered passageway portion 46a. The quality of the foam is firstly a function of its thickness and secondly a function of its rate of flow of the foamed material, since at the widest angle of the stream issuing from the orifice 42 the friction developed between the foamed material and the walls of the nozzle attachment can reduce the flow rate to an unacceptably low level.

The cylindrical body 40 in which the pressure reducing member 44 is mounted could terminate at a point near the outlet end of the throat portion 46b of the pressure reducing passageway of the member 44. However. in accordance with the present invention, as previously indicated it was discovered that a greatly increased foaming action is achieved by selecting a cylindrical body 40 with a length so it extends beyond the end of the point where the air pressure reducing passageway of the member 44 terminates, to provide an expansion chamber 41. However, the expansion chamber 41 has little or no effect in creating an overall enhanced foaming action when the liquid discharged from the end of the pressure reducing member 44 has not yet been foamed, so that the main benefit of the expansion chamber 41 is in its combination with a foam producing nozzle in advance of the same (which distinguishes it from the expansion chamber in the foam generating nozzle ofU.S. Pat. No. 3,701,482 where the expansion chamber thereof initially creates the foaming action). The expansion chamber 4 is desirably a cylindrical chamber with a width or diameter at least twice and preferably about three times the diameter or width of the throat portion 46b.

While the length to diameter ratios of the various passageways and chambers described may vary widely. there are extremes of these ratios which can destroy the operability of the foam generating nozzle attachment. For example, the length to diameter ratio of the throat portion 46b of the pressure reducing passageway of the member 44 is approximately 4 to 1, but if the length of the throat portion 46b were to be greatly extended, while a greater contact time between the liquid and the pressure reducing passageway may cause increased foam thickness, the frictional forces involved can reduce the flow velocity to a point where the foamed ma terial will be discharged with insufficient force to travel to the surface to be cleaned and, for all practical purposes, the nozzle attachment would be useless. Similarly, if the; length to diameter ratio of the expansion chamber 41 were to be increased materially from an optimum length, the frictional forces involved would reduce the velocity of the foamed material discharged from the end of the nozzle attachment to a point where an inadequate quantity of the material will reach the surface to be cleaned. FIG. 16 illustrates the variation of foam quality with the length to diameter ratio of the expansion chamber 41 and illustrates a substantial improvement of foam quality for length to diameter ratios of from about 7 to about 20, and particularly in the preferred range of from about 10 to about 16.

FIGS. 8A8B and 9A-9B illustrate differences in foam quality for two degrees of adjustment of the spray angle adjusting member 33c. Thus, FIG. 8A shows the forms a relatively thin foam layer 51 on the vertical wall surface 50 where the bubbles of the foam are relatively large. It can be seen from FIG. 8B. which illustrates the appearance of the foam layer on the vertical wall surface 50 several seconds later. that a substantial portion of the foam bubbles have broken. releasing the liquid portion thereof which runs down the vertical wall surface 50. FIG. 9A shows the consistency of the foam sprayed from the foam generating attachment 33!; upon a vertical wall surface 50 for an adjustment of the spray angle adjusting member 330 where the angle of divergence of the stream discharging from the orifice 42 is an optimum angle, which results in a forcefully applied very thick. fine bubble foam layer 51' on the vertical wall surface 50. In such case, as shown in FIG. 98, several seconds later the foam still remains as a thick layer upon the vertical wall surface.

FIG. 10 illustrates the condition of the foam discharging from the foam generating nozzle attachment 33b for an adjustment of the spray angle adjusting member 330 where the angle of divergence of the stream discharging from the orifice 42 is a maximum where, as previously indicated, the friction between the liquid and the defining walls of the pressure reducing passageway is such that, while a thick foam is achieved. the foam merely drips from the end of the nozzle attachment so it cannot reach the vertical wall surface The forms of the invention described thus provide very flexible foam generating means providing a selective thickness of the foam under varying pressure and spray material conditions.

It should be understood that numerous modifications may be made to the form of the invention described without deviating from the broader aspects of the invention.

We claim:

1. A foam generating nozzle assembly comprising: in combination: an inlet section through which a liquid can pass and including orifice-forming means through which liquid passes; and a foam-producing section having an inlet end which receives a stream issuing from said orifice-forming means. a pressure reducing passageway with a low pressure portion communicating with said inlet end, air inlet port-forming means in communication between the exterior of the nozzle assembly and said pressure reducing passageway, said pressure reducing passageway when said stream passes therethrough causing the aspiration of air through said air inlet port-forming means and the mixing thereof into the liquid stream passing through the nozzle assembly. the shape and dimension of said pressure reducing passageway being such that foam-producing turbulence is produced in the aerated stream passing therethrough, and a foam thickness enhancing expansion chamber beyond said pressure reducing passageway which expansion chamber has a widthat least about two times that of the low pressure portion of said pressure reducing passageway, the length to diameter ratio of said expansion chamber being in the range from about 7 to 20 so that the foamed material issuing from the end of said pressure reducing passageway is thickened substantially without substantially reducing the velocity thereof. 1 v g 2. The foam-generating nozzle. assembly of claim 1 wherein the length to diameter ratio of said expansion chamber is in the range from about 10 to 16.

3. The foam-generating nozzle assembly of claim 1 wherein said pressure reducing passageway includes an outwardly tapering portion merging with a throat portion which is said low pressure portion thereof.

'4. The foam generating nozzle assembly of claim 1 wherein said inlet section of said nozzle assembly is adapted to pass an unaerated liquid stream through said orifice-forming means.

5. in an adjustable foam-generating nozzle assembly comprising, in combination: an inlet section through which liquid can pass and including an orifice-forming means through which liquid passes with an outwardly diverging shape; a foam-producing section including an inlet end which receives the stream issuing from said outlet orifice-forming means, a pressure reducing passageway communicating with said inlet end, said pressure reducing passageway including an outwardly tapering portion merging with a throat portion, and air inlet port-forming means in communication between the exterior of the nozzle assembly and said pressure reducing passageway, said pressure-reducing passageway when said stream passes therethrough causing the aspiration of air through said air inlet port-forming means and the mixing thereof into the liquid streampassing through the nozzle assembly, and manually adjustable means for progressively varying the portions of .said pressure reducing passageway initially struck by the diverging stream issuing from said outlet orificeforming means so the widest portion of said diverging stream selectively can be made to strike at least one part of said outwardly tapering portion thereof and other portions of said passageway which vary the thick- 'ness ofthe foam stream discharged from said assembly substantially from a relatively thin to a relatively thick foam, the improvement wherein said foam-producing section includes a foam thickness enhancing expansion chamber beyond said pressure reducing passageway which expansion chamber has a width at least about twice that of the forward end portion of said pressure reducing passageway, and the length of said expansion chamber being sufficiently great that the foamed mate- 1 rial issuing from the end of saidpressure reducing pas- ;sageway is thickenedsubstantially without substantiail reducing the velocity thereof.

6. The foam-generating nozzle assembly of claim 5 wherein the length to diameter ratio of said expansion chamber is in'the range from about 7 to 20.

7. The foam-generating nozzle assembly of claim 5 .wherein the length to diameter ratio of said expansion chamber is inthe range from about 10 to 16.

8. An adjustable foam-generating nozzle assembly comprising, in combination: an inlet section through which an unaerated liquid can pass and including an adjustable portion with manually adjustable means comprising a rotatable member, a foam-producing section carried by said .rotatable member, said foam producing section having an inlet end which receives the entire variably shaped stream issuing from said ori flee-forming means, a pressure reducing passageway communicating with said inlet end, air inlet portforming means in communication between the exterior of the nozzle assembly and said pressure reducing passageway. said pressure reducing passageway when said stream passes therethrough causing the aspiration ofair through said air inlet port-forming means and the mixing thereof into the liquid stream passing through the nozzle assembly, the shape and. dimension of said pressure reducing passageway being such that foamproducing turbulence is produced in the aerated stream passing therethrough to a degree which varies with the shape of the stream issuing from said orifice-forming means of the nozzle assembly, and an expansion chamber beyond said pressure reducing passageway which expansion chamber has a width much greater than that of the forward end portion of said pressure-reducing passageway, and the length of said expansion chamber being sufficiently great that the foamed material issuing from the end of said pressure reducing passageway is thickened substantially without substantially reducing the velocity thereof.

9. An attachment for a non-foaming liquid spray nozzle unit including an outlet section through which unaerated liquid can pass and including an adjustable portion with manually adjustable means and orificeforming means through which unaerated liquid passes so the portion of a passageway located beyond said oriflee-forming means struck by the stream issuing therefrom will vary as the manually adjustable means is var ied; the attachment comprising a body portion attachable to the non-foaming liquid spray nozzle and having an inlet for receiving the variably shaped stream issuing from said orifice-forming means of said non-foaming spray nozzle unit, a foam producing pressure reducing passageway communicating with said inlet and positioned to receive the stream issuing from said orificeforming means so different portions thereof are struck thereby as said manually adjustable means is varied, air inlet port-forming means in communication between the exterior of the attachment and said pressure reducing passageway, said pressure reducing passageway when said stream passes therethrough causing the aspiration of air through said air inlet port-forming means and the mixing thereof into the liquid stream passing through the attachment,- the position, shape and dimension of said pressure reducing .passageway being such that foam-producing turbulence is produced in the aerated stream passing therethrough to a degree which varies with the points thereof struck by the stream issuing from said orifice-forming means so the thickness of the foam is substantially variable, and a foam enhancing chamber beyond said pressure reducing passageway which expansion chamber has a width much greater than that of the forward end portion of said pressure reducing passageway, the length to diameter ratio of said expansion chamber being in the range from about 7 to 20 so that the foamed material issuing from the end of said pressure reducing passageway is thickened substantially without substantially reducing the velocity thereof. 

1. A foam generating nozzle assembly comprising: in combination: an inlet section through which a liquid can pass and including orifice-forming means through which liquid passes; and a foamproducing section having an inlet end which receives a stream issuing from said orifice-forming means, a pressure reducing passageway with a low pressure portion communicating with said inlet end, air inlet port-forming means in communication between the exterior of the nozzle assembly and said pressure reducing passageway, said pressure reducing passageway when said stream passes therethrough causing the aspiration of air through said air inlet port-forming means and the mixing thereof into the liquid stream passing through the nozzle assembly, the shape and dimension of said pressure reducing passageway being such that foam-producing turbulence is produced in the aerated stream passing therethrough, and a foam thickness enhancing expansion chamber beyond said pressure reducing passageway which expansion chamber has a width at least about two times that of the low pressure portion of said pressure reducing passageway, the length to diameter ratio of said expansion chamber being in the range from about 7 to 20 so that the foamed material issuing from the end of said pressure reducing passageway is thickened substantially without substantially reducing the velocity thereof.
 2. The foam-generating nozzle assembly of claim 1 wherein the length to diameter ratio of said expansion chamber is in the range from about 10 to
 16. 3. The foam-generating nozzle assembly of claim 1 wherein said pressure reducing passageway includes an outwardly tapering portion merging with a throat portion which is said low pressure portion thereof.
 4. The foam generating nozzle assembly of claim 1 wherein said inlet section of said nozzle assembly is adapted to pass an unaerated liquid stream through said orifice-forming means.
 5. In an adjustable foam-generating nozzle assembly comprising, in combination: an inlet section through which liquid can pass and including an orifice-forming means through which liquid passes with an outwardly diverging shape; a foam-producing section including an inlet end which receives the stream issuing from said outlet orifice-forming means, a pressure reducing passageway communicating with said inlet end, said pressure reducing passageway including an outwardly tapering portion merging with a throat portion, and air inlet port-forming means in communication between the exterior of the nozzle assembly and said pressure reducing passageway, said pressure-reducing passageway when said stream passes therethrough causing the aspiration of air through said air inlet port-forming means and the mixing thereof into the liquid stream passing through the nozzle assembly, and manually adjustable means for progressively varying the portions of said pressure reducing passageway initially struck by the diverging stream issuing from said outlet orifice-forming means so the widest portion of said diverging stream selectively can be made to strike at least one part of said outwardly tapering portion thereof and other portions of said passageway which vary the thickness of the foam stream discharged from said assembly substantially from a relatively thin to a relatively thick foam, the improvement wherein said foam-producing section includes a foam thickness enhancing expansion chamber beyond said pressure reducing passageway which expansion chamber has a width at least about twice that of the forward end portion of said pressure reducing passageway, and the length of said expansion chamber being sufficiently great that the foamed material issuing from the end of said pressure reducing passageway is thickened substantially without substantially reducing the velocity thereof.
 6. The foam-generating nozzle assembly of claim 5 wherein the length to diameter ratio of said expansion chamber is in the range from about 7 to
 20. 7. The foam-generating nozzle assembly of claim 5 wherein the length to diameter ratio of said expansion chamber is in the range from about 10 to
 16. 9. An attachment for a non-foaming liquid spray nozzle unit including an outlet section through which unaerated liquid can pass and including an adjustable portion with manually adjustable means and orifice-forming means through which unaerated liquid passes so the portion of a passageway located beyond said orifice-forming means struck by the stream issuing therefrom will vary as the manually adjustable means is varied; the attachment comprising a body portion attachable to the non-foaming liquid spray nozzle and having an inlet for receiving the variably shaped stream issuing from said orifice-forming means of said non-foaming spray nozzle unit, a foam producing pressure reducing passageway communicating with said inlet and positioned to receive the stream issuing from said orifice-forming means so different portions thereof are struck thereby as said manually adjustable means is varied, air inlet port-forming means in communication between the exterior of the attachment and said pressure reducing passageway, said pressure reducing passageway when said stream passes therethrough causing the aspiration of air through said air inlet port-forming means and the mixing thereof into the liquid stream passing through the attachment, the position, shape and dimension of said pressure reducing passageway being such that foam-producing turbulence is produced in the aerated stream passing therethrough to a degree which varies with the points thereof struck by the stream issuing from said orifice-forming means so the thickness of the foam is substantially variable, and a foam enhancing chamber beyond said pressure reducing passageway which expansion chamber has a width much greater than that of the forward end portion of said pressure reducing passageway, the length to diameter ratio of said expansion chamber being in the range from about 7 to 20 so that the foamed material issuing from the end of said pressure reducing passageway is thickened substantially without substantially reducing the velocity thereof. 